Ratty Bug
A ladybug crossed with a rat. The first enemy in the game, and the one that teaches the sword.
It scurries, it is small, and it dies in one clean hit if that hit is a slash. It exists to make the rusted sword feel good before the crypt takes that feeling away.
Where it matters is grouping. A single ratty bug is a free hit; two of them arriving from different angles is the first time the stamina bar becomes a problem rather than a curiosity. Kill the first, and the swing that killed it has already spent the budget you needed for the second. The fix is not a better sword, it is a thrown dagger or a retreat, and the demo teaches that on the beach rather than in the crypt.
It is also the cleanest demonstration of why damage type is not a stat but a match-up. The bug is not armoured, not fast, and not evasive; it simply has a body that a blade opens. Nothing about that encounter would be improved by a longer paragraph of numbers, which is why this entry stays short on purpose.